Spined or slit fins are formed from flat stock with cuts made uniformly along each side and with the central portion left intact. The slit flat stock is then bent into a U-shaped configuration with the central un-cut portion serving as the bight or base. The U-shaped slit stock is spirally wrapped about the tubing and is glued or otherwise suitably secured to the tubing with the base or bight in metal-to-metal contact with the tubing. This results in the tubing being covered with radiating spines or tines to produce slit fin tubing stock suitable for use as heat exchange coils.
Conventionally, the slit fin tubing stock has been wrapped around a forming drum with the wraps in a parallel abutting relation to each other to form a plurality of helically wound circuits which, in turn, make up the coil. Terminal leads are provided at each end of the circuits. The forming drum is then removed. Terminal leads at each end of the circuits of the coil are bent, disposed one inwardly of the other so that they are positioned tangent to the same plane, which is perpendicular to the center longitudinal axis of the coil, and then a portion of each terminal lead is cut off and joined to a header. Due to the fragility of the individual spines or tines, any subsequent forming of the coil has been precluded.